Dermatitis is an inflammatory disease at the skin against various kinds of endogenetic and exogenetic invasion, and the disease includes atopic dermatitis, contact dermatitis, seborrheic dermatitis, nummular eczema, autosensitization eczema and the like. These dermatitises accompany itching in many cases. Also, of these, atopic dermatitis is a refractory chronic inflammatory disease which repeats remission and exacerbation, and involvement of a late phase reaction that accompanies invasion of eosinophils or lymphocyte and production of various kinds of cytokines at a site of inflammation has been suggested for pathogeny and chronicity of the disease (Non-Patent Literatures 1 and 2).
For the treatment of atopic dermatitis, a treatment by a medicament depending on the symptom has been employed in combination with removal of factors of causing diseases or exacerbation and skin care, and a topical steroid agent has mainly been used against inflammation. Also, tacrolimus which is a kind of an immunosuppressive agent has recently been used for the treatment of atopic dermatitis. However, these existing medicaments are not necessarily satisfied in the points of safety and side effects. Thus, it has been desired to develop a therapeutic agent for dermatitis not only having effectiveness but also high safety.
It has been known that Compound [I] which is an active ingredient of the present invention has selective phosphodiesterase IV (PDE IV) inhibitory activity, and useful as an agent for prophylaxis and treatment of asthma and the like. (Patent Literatures 1 and 2). However, it has not been reported that said Compound [I] is useful as an agent for treatment of dermatitis such as atopic dermatitis and the like.    Patent Literature 1: EP 748,805 B (p. 2)    Patent Literature 2: EP 848,000 B (p. 2)    Non-Patent Literature 1: Iwamoto et al., J. Leukoc. Biol., Vol. 52, pp. 572-578 (1992)    Non-Patent Literature 2: Frigas et al., J. Allergy Clin. Immunol., Vol. 77, pp. 527-537 (1986)